Liquid crystal display device

ABSTRACT

In a liquid crystal display device, a light shielding film, a color filter, an overcoat film, and an alignment film are formed in this order on a counter substrate. However, the alignment film is not formed in a seal portion. When the alignment film is subjected to photo-alignment with ultraviolet radiation, a portion of the overcoat film not covered with the alignment film is degraded by ultraviolet radiation. In order to prevent moisture penetrating from the degraded overcoat film from reaching the light shielding film to thereby alter the light shielding film and from causing the peeling of the light shielding film, the color filter is disposed below the overcoat film to block the moisture.

CLAIM OF PRIORITY

This application is a continuation of U.S. application Ser. No.12/832,221, filed Jul. 8, 2010 and which application claims priorityfrom Japanese application serial No. 2009-161616 filed on Jul. 8, 2009,the content of which is hereby incorporated by reference into thisapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device and more particularlyto an in-plane switching (IPS) type liquid crystal display deviceimproved in reliability of a seal portion.

2. Description of the Related Art

A liquid crystal display device includes a TFT substrate on which pixelelectrodes, thin film transistors (TFTs), and the like are formed in amatrix, a counter substrate which is disposed to face the TFT substrateand on which color filters and the like are formed at positionscorresponding to the pixel electrodes of the TFT substrate, and liquidcrystal interposed between the TFT substrate and the counter substrate.An image is formed by controlling the transmittance ratio of lightthrough liquid crystal molecules for each pixel.

The liquid crystal display device is flat and light in weight, andtherefore the application of liquid crystal display device has expandedin various fields from large display devices such as TVs to smalldisplay devices such as mobile phones or digital still cameras (DSCs).On the other hand, the liquid crystal display device has a problem ofviewing angle characteristics. Viewing angle characteristics refer to aphenomenon where brightness varies or chromaticity varies between when ascreen is seen from the front and when the screen is seen from adiagonal direction. The IPS type, in which the liquid crystal moleculesare moved by a horizontal direction electric field, has excellentviewing angle characteristics.

In the IPS type, it is not necessary to form a pretilt angle for liquidcrystal molecules in the vicinity of an alignment film. Therefore, analignment axis for the alignment film can be formed not by a rubbingmethod but by a photo-alignment method. The photo-alignment has such anadvantage that it does not cause static electricity compared to therubbing method, for example.

The photo-alignment imparts anisotropy to an alignment film with theirradiation of polarized ultraviolet radiation so that liquid crystalmolecules are aligned in a specific direction with respect to thealignment film. JP-A-2005-351924 describes a technique relating to thephoto-alignment described above.

The photo-alignment is performed by irradiating an alignment film madeof a polymer with ultraviolet radiation polarized in a specificdirection. For example, when the polymer formed in a network isirradiated with polarized ultraviolet radiation, the polymer in aspecific direction with respect to the polarized direction ofultraviolet radiation is damaged. This can form anisotropy for thealignment film for aligning liquid crystal molecules. There is noproblem when only the alignment film is irradiated with polarizedultraviolet radiation for photo-alignment. However, when a portion otherthan the alignment film is irradiated, the irradiated portion isdegraded by the ultraviolet radiation, causing problems.

IPS type liquid crystal display devices have been used for small liquidcrystal display devices. Manufacturing small liquid crystal displaydevices one by one is inefficient. Therefore, a number of liquid crystaldisplay devices are formed on a mother substrate to simultaneouslymanufacture a number of liquid crystal display devices.

FIG. 13 shows an example where 35 small liquid crystal display cells 1are prepared on a mother substrate. A mother TFT substrate 1000 on whicha number of TFT substrates 100 each having TFTs and pixel electrodes areformed, and a mother counter substrate 2000 on which a number of countersubstrates 200 each having color filters and the like formed thereon areformed are aligned to each other. The mother TFT substrate 1000 and themother counter substrate 2000 are bonded together with sealing materials15 and a mother substrate sealing material 151. In FIG. 13, each ofhatched rectangles surrounded by the sealing material 15 indicates arange where an alignment film 113 is formed.

Small liquid crystal display devices are required to be thin. Forexample, the TFT substrate and the counter substrate each has athickness of about 0.2 mm. However, such thin glass does not exist as astandard product. Moreover, such a thin glass substrate cannot undergothe process at present. Accordingly, in a state of the mother countersubstrate 2000 or the mother TFT substrate 1000, glass having athickness of about 0.5 mm is used, and after the mother countersubstrate 2000 and the mother TFT substrate 1000 are aligned to eachother to form a mother substrate, the outer surface of the mothercounter substrate 2000 or the mother TFT substrate 1000 is polished.

Polishing is often carried out with a combination of mechanicalpolishing and chemical polishing. In both mechanical polishing andchemical polishing, when abrasive enters the inside of the mothersubstrate, the liquid crystal cells 1 inside of the mother substratebecome defective. Therefore, the inside of the mother substrate isprotected by the mother substrate sealing material 151. The mothersubstrate sealing material 151 formed at the periphery of the mothersubstrate is sealed with a mother-substrate end-sealing material 161.The mother substrate shown in FIG. 13 is separated into individualliquid crystal cells after polishing. FIG. 14 shows the mother countersubstrate 2000 constituting the mother substrate shown in FIG. 13, inwhich 35 counter substrates 200 are formed corresponding to the liquidcrystal cells 1 in FIG. 13. FIG. 14 shows the mother counter substrate2000 at a stage before forming the sealing materials 15 or the mothersubstrate sealing material 151 thereon. In FIG. 14, the alignment film113 is formed on each of the counter substrates 200. Since the presenceof the alignment film in a seal portion reduces the adhesive force ofthe sealing material 15, the alignment film 113 is formed so as to avoidthe seal portion and cover a display region.

In FIG. 14, the alignment film 113 is formed by flexographic printing.After forming the alignment film 113, photo-alignment is performed onthe alignment film 113 using polarized ultraviolet radiation. At thistime, the entire surface of the mother counter substrate 2000 isirradiated with polarized ultraviolet radiation. This is becauseirradiation of the alignment films with polarized ultraviolet radiationone by one increases the manufacturing cost. Accordingly, also a portionwhere the alignment film is not formed is irradiated with polarizedultraviolet radiation.

FIG. 15 is a cross-sectional structure of one counter substrate 200 atan edge portion, showing a state of irradiation of polarized ultravioletradiation for the photo-alignment. At the edge portion of the countersubstrate 200, a light shielding film 202, a color filter 201, anovercoat film 203, and the like are formed as will be described later.The light shielding film 202 has a function to improve the contrast of ascreen or to enhance the appearance of the screen periphery and is alsoreferred to as black matrix. In the specification, however, the term“light shielding film” is used. As shown in FIG. 15, at a portion wherethe alignment film 113 is not present, a hatched portion 2031 of theovercoat film 203 is directly irradiated with ultraviolet radiation.Therefore, this portion 2031 of the overcoat film is degraded, wherebythe overcoat film 203 allows moisture to easily penetrate.

FIG. 16 is a cross-sectional view of an edge portion of the countersubstrate 200, showing a state where after performing thephoto-alignment using polarized ultraviolet radiation, the sealingmaterial 15 is formed. Since the hatched portion 2031 of the overcoatfilm 203 is degraded by ultraviolet radiation, moisture penetratesthrough this portion 2031 of the overcoat film to the surface of thelight shielding film 202.

FIG. 17 is a cross-sectional view of an edge portion of a liquid crystaldisplay panel in a state where the TFT substrate 100 and the countersubstrate 200 are bonded together, and liquid crystal layer 300 issealed therebetween. In FIG. 17, an inorganic passivation film 106, anorganic passivation film 107, and the alignment film 113 are formed onthe TFT substrate 100. The light shielding film 202, the color filter201, the overcoat film 203, and the alignment film 113 are formed on thecounter substrate 200. In FIG. 17, since the hatched portion 2031 of theovercoat film 203 of the counter substrate 200 is degraded byultraviolet radiation in the photo-alignment, moisture easily entersthis portion from the outside.

When moisture enters the degraded overcoat film 2031, the moisturereaches the light shielding film 202 and alters the light shielding film202. Especially when moisture acts on the light shielding film 202, theadhesive force between the light shielding film 202 and the substrates200 is reduced, which reduces the reliability in the seal portion.Moreover, when moisture acts on the light shielding film 202, theelectrical resistance of the light shielding film 202 is reduced, anelectric field in the liquid crystal layer 300 is disturbed by theinfluence of the light shielding film 202, and the contrast is reducedby light leakage.

SUMMARY OF THE INVENTION

It is an object of the invention to prevent moisture entering from theoutside due to an overcoat film degraded by irradiation of ultravioletradiation in photo-alignment from affecting a light shielding film.

To achieve the above-described object, the invention is specificallyconfigured as follows.

(1) A liquid crystal display device includes: a TFT substrate having adisplay region where pixels each having a TFT and a pixel electrode areformed in a matrix; a counter substrate bonded to the TFT substrate witha sealing material in a seal portion at a periphery thereof and having adisplay region where a light shielding film and color filters of threecolors are formed, an overcoat film is formed so as to cover the colorfilters of three colors, and an alignment film is formed so as to coverthe overcoat film; and liquid crystal sealed between the TFT substrateand the counter substrate, wherein in the counter substrate, thealignment film is subjected to an alignment treatment byphoto-alignment, and the alignment film is not formed in the sealportion; and in the seal portion of the counter substrate, the lightshielding film, a color filter of one color among the color filters ofthree colors, and the overcoat film are stacked in this order, and thesealing material is formed on the overcoat film.

(2) A liquid crystal display device includes: a TFT substrate having adisplay region where pixels each having a TFT and a pixel electrode areformed in a matrix; a counter substrate bonded to the TFT substrate witha sealing material in a seal portion at a periphery thereof and having adisplay region where a light shielding film and color filters of threecolors are formed, an overcoat film is formed so as to cover the colorfilters of three colors, and an alignment film is formed so as to coverthe overcoat film; and liquid crystal sealed between the TFT substrateand the counter substrate, wherein in the counter substrate, thealignment film is subjected to an alignment treatment byphoto-alignment, and the alignment film is not formed in the sealportion; and in the seal portion of the counter substrate, the lightshielding film and color filters of a plurality of colors among thecolor filters of three colors are stacked, the overcoat film is formedso as to cover the stacked color filters, and the sealing material isformed on the overcoat film.

(3) The liquid crystal display device according to (2), wherein one ofthe plurality of color filters formed in the seal portion is formedcontinuously with the color filter formed in the display region, and theother color filters among the plurality of color filters arediscontinuous with the color filters formed in the display region.

(4) A liquid crystal display device includes: a TFT substrate having adisplay region where pixels each having a TFT and a pixel electrode areformed in a matrix; a counter substrate bonded to the TFT substrate witha sealing material in a seal portion at a periphery thereof and having adisplay region where a light shielding film and color filters of threecolors are formed, an overcoat film is formed so as to cover the colorfilters of three colors, and an alignment film is formed so as to coverthe overcoat film; and liquid crystal sealed between the TFT substrateand the counter substrate, wherein in the counter substrate, thealignment film is subjected to an alignment treatment byphoto-alignment, and the alignment film is not formed in the sealportion; in the seal portion of the counter substrate, the lightshielding film, a color filter of one color among the color filters ofthree colors, and the overcoat film are stacked in this order; the colorfilter of one color formed in the seal portion is formed discontinuouslywith any of the color filters of three colors formed in the displayregion; a step is formed on the overcoat film corresponding to an edgeof the color filter of one color formed in the seal portion; and thesealing material is formed on the overcoat film.

(5) A liquid crystal display device includes: a TFT substrate having adisplay region where pixels each having a TFT and a pixel electrode areformed in a matrix; a counter substrate bonded to the TFT substrate witha sealing material in a seal portion at a periphery thereof and having adisplay region where a light shielding film and color filters of threecolors are formed, an overcoat film is formed so as to cover the colorfilters of three colors, and an alignment film is formed so as to coverthe overcoat film; and liquid crystal sealed between the TFT substrateand the counter substrate, wherein in the counter substrate, thealignment film is subjected to an alignment treatment byphoto-alignment, and the alignment film is not formed in the sealportion; in the seal portion of the counter substrate, the lightshielding film and color filters of a plurality of colors among thecolor filters of three colors are stacked, and the overcoat film isformed so as to cover the stacked color filters; the plurality of colorfilters formed in the seal portion are formed discontinuously with anyof the color filters of three colors formed in the display region; astep is formed on the overcoat film corresponding to an edge of theplurality of color filters formed in the seal portion; and the sealingmaterial is formed on the overcoat film.

(6) A liquid crystal display device includes: a TFT substrate having adisplay region where pixels each having a TFT and a pixel electrode areformed in a matrix; a counter substrate bonded to the TFT substrate witha sealing material in a seal portion at a periphery thereof and having adisplay region where a light shielding film and color filters of threecolors are formed, an overcoat film is formed so as to cover the colorfilters of three colors, and an alignment film is formed so as to coverthe overcoat film; and liquid crystal sealed between the TFT substrateand the counter substrate, wherein in the counter substrate, thealignment film is subjected to an alignment treatment byphoto-alignment, and the alignment film is not formed in the sealportion; in the seal portion of the counter substrate, the lightshielding film and the overcoat film are stacked in this order; athickness of the overcoat film at the seal portion is greater than thatof the overcoat film at the display region; and the sealing material isformed on the overcoat film.

(7) The liquid crystal display device according to (6), wherein athickness of the overcoat film at the seal portion is equal to orgreater than 1.5 times that of the overcoat film at the display region.

According to an aspect of the invention, even when an overcoat film at aseal portion is degraded by ultraviolet radiation in photo-alignment,and moisture penetrates into the degraded overcoat film, the moisturecan be blocked by a color filter disposed below the overcoat film andhardly reaches the light shielding film. Therefore, it is possible toprevent the peeling of the light shielding film. Moreover, since areduction in electrical resistance of the light shielding film can beprevented, it is possible to prevent a reduction in contrast due tolight leakage of a liquid crystal layer.

According to another aspect of the invention, since the overcoat film isformed thicker at the seal portion than at a display region, theovercoat film can be prevented from being entirely degraded byultraviolet radiation in photo-alignment. Therefore, it is possible toprevent moisture from reaching the light shielding film. Moreover, sincethe overcoat film is not thick at the display region, it is possible toprevent a reduction in brightness of a display screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a liquid crystal display device.

FIG. 2 is a cross-sectional view of a display region of the liquidcrystal display device.

FIG. 3 is a cross-sectional view of a seal portion of a liquid crystaldisplay device according to a first embodiment.

FIG. 4 is a cross-sectional view of a counter substrate inphoto-alignment.

FIG. 5 is a cross-sectional view of a counter substrate according to thefirst embodiment.

FIG. 6 is a cross-sectional view of a counter substrate according to asecond embodiment.

FIG. 7 is a cross-sectional view of a counter substrate according toanother aspect of the second embodiment.

FIG. 8 is a cross-sectional view of a counter substrate according to athird embodiment.

FIG. 9 is a cross-sectional view of a counter substrate according to afourth embodiment.

FIG. 10 is a cross-sectional view of a counter substrate according toanother aspect of the fourth embodiment.

FIG. 11 is a cross-sectional view of a counter substrate according to afifth embodiment.

FIG. 12 is a cross-sectional view of a counter substrate according toanother aspect of the fifth embodiment.

FIG. 13 is a plan view of a mother substrate.

FIG. 14 is a plan view of a mother counter substrate.

FIG. 15 is a cross-sectional view of a counter substrate inphoto-alignment in the related art.

FIG. 16 is a cross-sectional view of the counter substrate in a statewhere a sealing material is formed in the related art.

FIG. 17 is a cross-sectional view of an edge portion of a liquid crystaldisplay device in the related art.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the contents of the invention will be described in detailbased on embodiments.

First Embodiment

FIG. 1 is a plan view of a small liquid crystal display device used formobile phones or the like as an example of a product to which theinvention is applied. In FIG. 1, a counter substrate 200 is disposedabove a TFT substrate 100. A liquid crystal layer is interposed betweenthe TFT substrate 100 and the counter substrate 200. The TFT substrate100 and the counter substrate 200 are bonded together with a sealingmaterial 15 formed in a frame portion. In FIG. 1, a filling port isformed in the sealing material 15, and liquid crystal is filled throughthe filling port. Thereafter, the filling port is sealed with anend-sealing material 16.

The TFT substrate 100 is formed larger than the counter substrate 200.In a portion of the TFT substrate 100 extended from the countersubstrate 200, a terminal portion 150 for supplying a power supply,video signals, scanning signals, and the like to a liquid crystaldisplay panel is formed. In the terminal portion 150, an IC driver 50for driving scanning lines, video signal lines, and the like isdisposed. The IC driver 50 is divided into three regions. At the centerof the IC driver, a video signal drive circuit 52 is disposed. Ascanning signal drive circuit 51 is disposed on both sides of thecenter.

In a display region 10 of FIG. 1, scanning lines 30 extend in thehorizontal direction and are arranged in the vertical direction.Moreover, video signal lines 40 extend in the vertical direction and arearranged in the horizontal direction. The scanning lines 30 areconnected to the scanning signal drive circuit 51 of the IC driver 50through scanning-line lead lines 31. In FIG. 1, for arranging thedisplay region 10 at the center of the liquid crystal display device,the scanning-line lead lines 31 are arranged on both sides of thedisplay region 10. Therefore, the scanning signal drive circuit 51 isdisposed on both sides in the IC driver 50. On the other hand,video-signal-line lead lines 41 which connect the video signal lines 40with the IC driver are collected on the lower side of a screen. Thevideo-signal-line lead lines 41 are connected to the video signal drivecircuit 52 arranged at the central portion of the IC driver 50.

An alignment film 113 is formed in a region slightly larger than thedisplay region 10 in FIG. 1. Photo-alignment is performed on thealignment film 113. The alignment film 113 is not formed at a portionwhere the sealing material 15 is formed. This is because the presence ofthe alignment film 113 reduces the adhesive force between the sealingmaterial 15 and the substrate.

FIG. 2 is a cross-sectional view showing the structure of an IPS typeliquid crystal display device in a display region. Various electrodestructures of IPS type liquid crystal display devices have been proposedand put to practice use. The structure of FIG. 2 has been widely used atpresent. Briefly speaking, a pixel electrode 110 having a comb-teethshape is formed above a counter electrode 108 which is formed in aplanar and solid manner with an inter-layer insulating film 109interposed therebetween. Liquid crystal molecules 301 are rotated by avoltage between the pixel electrode 110 and the counter electrode 108 tocontrol the transmittance ratio of light in a liquid crystal layer 300for each pixel, whereby an image is formed. The structure of FIG. 2 willbe described in detail below. Although the invention is described bytaking the configuration of FIG. 2 as an example, the invention can alsobe applied to IPS type liquid crystal display devices other than that ofFIG. 2.

In FIG. 2, a gate electrode 101 is formed on the TFT substrate 100formed of glass. The gate electrode 101 is formed in the same layer asthe scanning lines. The gate electrode 101 includes an AlNd alloy layerand a MoCr alloy layer stacked in this order.

A gate insulating film 102 is formed of SiN so as to cover the gateelectrode 101. A semiconductor layer 103 is formed of an a-Si film onthe gate insulating film 102 at a position facing the gate electrode101. The a-Si film is formed by plasma CVD. The a-Si film forms achannel portion of a TFT. A source electrode 104 and a drain electrode105 are formed on the a-Si film with the channel portion interposedbetween the source electrode and the drain electrode. A not-shown n+Silayer is formed between the a-Si film and the source electrode 104 orthe drain electrode 105 for establishing ohmic contact between thesemiconductor layer and the source electrode 104 or the drain electrode105.

The source electrode 104 is also used as the video signal line, and thedrain electrode 105 is connected to the pixel electrode 110. The sourceelectrode 104 and the drain electrode 105 are formed simultaneously inthe same layer. In the embodiment, the source electrode 104 or the drainelectrode 105 is formed of a MoCr alloy. For reducing the electricalresistance of the source electrode 104 or the drain electrode 105, anelectrode structure having an AlNd alloy layer sandwiched between MoCralloy layers is used.

An inorganic passivation film 106 is formed of SiN so as to cover theTFT. The inorganic passivation film 106 protects especially the channelportion of the TFT against impurities 401. An organic passivation film107 is formed on the inorganic passivation film 106. Since the organicpassivation film 107 functions to protect the TFT and planarize thesurface of the TFT, the film is formed thick. The thickness thereof isfrom 1 μm to 4 μm.

The counter electrode 108 is formed on the organic passivation film 107.The counter electrode 108 is formed by sputtering an indium tin oxide(ITO) film as a transparent conductive film over the entire displayregion. That is, the counter electrode 108 is formed in a planar manner.After the counter electrode 108 is formed by sputtering over the entiresurface, only a through hole 111 portion for establishing electricalcontinuity between the pixel electrode 110 and the drain electrode 105is formed by removing the counter electrode 108 by etching.

An inter-layer insulating film 109 is formed of SiN so as to cover thecounter electrode 108. After forming the inter-layer insulating film109, the through hole 111 is formed. Thereafter, an ITO film serving asthe pixel electrode 110 is deposited so as to cover the inter-layerinsulating film 109 and the through hole 111. The deposited ITO film ispatterned to form the pixel electrode 110. The ITO film serving as thepixel electrode 110 is also deposited on the through hole 111. In thethrough hole 111, the drain electrode 105 extended from the TFT and thepixel electrode 110 are electrically conducted, so that a video signalis supplied to the pixel electrode 110.

The pixel electrode is a so-called comb-teeth shaped electrode. A slit112 shown in FIG. 2 is formed between electrodes each having acomb-tooth shape. A fixed voltage is applied to the counter electrode108, and a voltage due to a video signal is applied to the pixelelectrode 110. As shown in 2, when the voltage is applied to the pixelelectrode 110, lines of electric force are generated to rotate theliquid crystal molecules 301 in a direction of the lines of electricforce, whereby the transmission of light from a backlight is controlled.The transmission of light from the backlight is controlled for eachpixel, whereby an image is formed. The alignment film 113 on the TFTsubstrate side is formed on the pixel electrode 110 to align the liquidcrystal molecules 301. Photo-alignment using polarized ultravioletradiation is employed as an alignment treatment for the alignment film.

In the example shown in FIG. 2, the counter electrode 108 formed in aplanar manner is disposed on the organic passivation film 107, and thecomb-teeth electrode 110 is disposed on the inter-layer insulating film109. Contrary to this, however, the pixel electrode 110 formed in aplanar manner may be disposed on the organic passivation film 107, andthe counter electrode 108 having a comb-teeth shape may be disposed onthe inter-layer insulating film 109.

In FIG. 2, the counter substrate 200 is disposed with the liquid crystallayer 300 interposed between the counter substrate 200 and the TFTsubstrate 100. Color filters are formed on the inner side of the countersubstrate 200. In FIG. 2, a red color filter 201R is formed. A lightshielding film 202 is formed below the color filter at a region where animage is not formed. The light shielding film 202 improves the contrastof image and also functions as the light shielding film of the TFT forpreventing photocurrent from flowing into the TFT.

An overcoat film 203 is formed so as to cover the red color filter 201Rand the light shielding film 202. Since the surface of the red colorfilter 201R and the light shielding film 202 has irregularities, thesurface is planarized by the overcoat film 203. An alignment film 113for determining the initial alignment of liquid crystal is formed on theovercoat film 203. The alignment film 113 is subjected to thephoto-alignment treatment.

Since FIG. 2 shows the IPS type liquid crystal display device, thecounter electrode 108 is formed on the TFT substrate 100 side but notformed on the counter substrate 200 side. In the IPS type as describedabove, a conductive film is not formed on the inner side of the countersubstrate 200. Therefore, the potential of the counter substrate 200becomes unstable. Moreover, electromagnetic noise from the outsideenters the liquid crystal layer 300 to exert an influence on an image.For eliminating the problems, a surface conductive film 210 is formed onthe outer surface of the counter substrate 200. The surface conductivefilm 210 is formed by sputtering an ITO film as a transparent conductivefilm.

FIG. 3 is a cross-sectional view of the liquid crystal display device atan edge portion shown in FIG. 1. In FIG. 3, the inorganic passivationfilm 106, the organic passivation film 107, and the alignment film 113are formed on the TFT substrate 100. The other configurations of the TFTsubstrate 100 are not illustrated in FIG. 3. The light shielding film202, the red color filter 201R, the overcoat film 203, and the alignmentfilm 113 are formed on the counter substrate 200. The edge portion issealed with the sealing material 15, and the gap between the TFTsubstrate 100 and the counter substrate 200 is defined by spacers 350made of glass fibers.

In FIG. 3, the alignment film 113 is subjected to the alignmenttreatment by photo-alignment. A feature of the invention shown in FIG. 3is in that the red color filter 201R is disposed below the overcoat film203 at the edge portion. While the red color filter 201R is formed inFIG. 3, a green color filter or a blue color filter may be formed. Inthe counter substrate 200 of FIG. 3, the overcoat film 203 at a portionwhere the alignment film 113 is not present is degraded by ultravioletradiation in photo-alignment, and therefore is in a state where moistureeasily enters the portion.

Even when the overcoat film 203 is degraded by ultraviolet radiation,the red color filter 201R is present below the overcoat film 203.Accordingly, the moisture entering the overcoat film 203 is blocked bythe red color filter 201R and does not reach the light shielding film202 situated below the overcoat film 203, or it takes long time for themoisture to reach the light shielding film 202. Accordingly, it ispossible to prevent a reduction in adhesive force or a reduction inelectrical resistance of the light shielding film 202 due to reaction ofthe light shielding film 202 with moisture.

FIGS. 4 and 5 illustrate the above description. FIG. 4 shows a statewhere the light shielding film 202, the red color filter 201R, theovercoat film 203, and the alignment film 113 are formed in this orderon the counter substrate 200. The light shielding film 202 has athickness of about 1 μm. The red color filter 201R has a thickness offrom 1 to 2 μm. The overcoat film 203 has a thickness of 1 to 2 μm. Thealignment film 113 has a thickness of about 0.1 μm. The green colorfilter, the blue color filter, and the like have also a thickness offrom 1 to 2 μm.

The alignment film 113 is not formed at the edge portion. This is forpreventing a reduction in adhesive force of the sealing material 15 dueto the alignment film 113. In FIG. 4, the alignment film 113 isirradiated with ultraviolet radiation UV for applying the alignmenttreatment. The alignment film 113 is subjected to the alignmenttreatment with ultraviolet radiation, but a hatched overcoat film 2031at the edge portion where the alignment film 113 is not present isdegraded by the ultraviolet radiation.

Thereafter, as shown in FIG. 5, the sealing material 15 is formed on theovercoat film 203 at the edge portion where the alignment film 113 isnot present. In FIG. 5, moisture easily penetrates into the hatchedportion 2031 of the overcoat film degraded by the ultraviolet radiation.However, since the red color filter 201R is present below the hatchedovercoat film 2031, the penetrated moisture is blocked by the red colorfilter 201R and does not easily reach the light shielding film 202.Accordingly, the reliability of the seal portion can be assured.

In the related art, a color filter is formed only in a display region.In the invention, however, a color filter is extended up to the edgeportion of the counter substrate 200. The color filter is formed byphotolithography. That is, the forming range of the color filter can bedefined by an exposure mask. Accordingly, even when the color filter isformed up to the edge portion of the counter substrate, the number ofprocesses does not increase.

According to the embodiment as described above, even when the overcoatfilm 203 is degraded by ultraviolet radiation in the photo-alignmenttreatment, the influence of moisture penetrating through the overcoatfilm 203 is blocked by the color filter. Therefore, the reliability ofthe seal portion is not reduced. Moreover, it is also possible toprevent a reduction in electrical resistance of the light shielding film202 caused by reaction of moisture with the light shielding film 202.Therefore, a reduction in contrast due to light leakage of liquidcrystal can be prevented.

In the above embodiment, although a color filter formed in the sealportion is the red color filter 201R, this is illustrative only. Anothercolor filter, that is, a green color filter or a blue color filter maybe formed.

Second Embodiment

FIG. 6 is a cross-sectional view of the counter substrate 200 in thevicinity of an edge portion according to a second embodiment of theinvention. In FIG. 6, the light shielding film 202, the red color filter201R, the overcoat film 203, and the alignment film 113 are formed inthis order on the counter substrate 200. However, the red color filter201R and a green color filter 201G are stacked in a seal portion wherethe alignment film 113 is not present. The alignment film 113 issubjected to the photo-alignment treatment. Accordingly, the overcoatfilm 203 at the portion where the alignment film 113 is not present isdegraded by ultraviolet radiation.

In FIG. 6, two layers of color filters of the green color filter 201Gand the red color filter 201R are formed below the overcoat film 203degraded by ultraviolet radiation. Accordingly, even when moisturepenetrates into the degraded overcoat film 203, the penetrated moistureis blocked by the green color filter 201G and the red color filter 201Rand does not reach the light shielding film 202.

In the configuration of FIG. 6, since the two layers of the colorfilters are formed in the seal portion, a protective effect againstmoisture is greater than that of the configuration of the firstembodiment. The respective layers have the same thicknesses as those ofthe first embodiment. That is, both the green color filter and the redcolor filter are formed to have a thickness of from 1 to 2 μm in thesame manner as in the first embodiment.

Another effect of the configuration of FIG. 6 is in that the entering ofthe alignment film 113 into the seal portion can be prevented when thealignment film 113 is applied. As shown in FIG. 6, since the green colorfilter 201G is formed in the vicinity of the edge portion, a step isproduced on the overcoat film 203. The step functions as a stopperagainst the alignment film 113 flowing from the display region.

The alignment film 113 has fluidity when applied because it is liquid,and therefore it is hard to accurately define the applying area.Especially the presence of the alignment film 113 below the sealingmaterial 15 reduces the adhesive force of the sealing material 15. Inthe embodiment, as shown in FIG. 6, since the range of the alignmentfilm 113 can be defined by forming the step with the green color filter201G, the reliability in the seal portion can be maintained at a highlevel. Since the green color filter 201G formed at the periphery isformed by photolithography, accurate dimension can be maintained. Thestep has a height of about from 1 to 2 μm, which is the thickness of thegreen color filter.

FIG. 7 shows another aspect in the embodiment. A display region on theleft of FIG. 7 is similar to that described with reference to FIG. 6,but an edge portion is different from that of FIG. 6. Between the lightshielding film 202 and the overcoat film 203, three layers of colorfilters of the red color filter 201R, the green color filter 201G, and ablue color filter 201B are formed in this order. The alignment film 113is subjected to the photo-alignment treatment in the same manner as inthe first embodiment or in FIG. 6.

In FIG. 7, the overcoat film 203 at a portion not covered with thealignment film 113 is degraded by ultraviolet radiation inphoto-alignment in the same manner as in the first embodiment. In theembodiment, since the three layers of the color filters are presentuntil moisture penetrating through the degraded overcoat film 203reaches the light shielding film 202, the reliability of the sealportion can be further improved more than that of FIG. 6.

As shown in FIG. 7, a step is formed with two layers of color filters ofthe green color filter 201G and the blue color filter 201B in thevicinity of the seal portion. Therefore, the forming range of thealignment film 113 can be defined by the step. In the embodiment, thestep is formed with the two layers of the color filters, and the stepcan be formed to have a height of from 2 μm to about 4 μm. Therefore,the applying range of the alignment film can be defined more reliably.

In the embodiment, although the red color filter 201R and the greencolor filter 201G are sequentially stacked in FIG. 6, two layers ofcolor filters are not limited to those color filters. Other colorfilters may be stacked, and the order of stacking may be different. Alsoin FIG. 7, although the color filters are stacked in the order of thered color filter 201R, the green color filter 201G, and the blue colorfilter 201B, the stacking order of color filters is not limited to thisbut can be arbitrarily determined depending on the manufacturingconditions of color filter.

Third Embodiment

FIG. 8 is a cross-sectional view of the counter substrate 200 in thevicinity of an edge portion according to a third embodiment. In FIG. 8,the light shielding film 202, the red color filter 201R, the overcoatfilm 203, and the alignment film 113 are formed in this order on thecounter substrate 200. The alignment film 113 is subjected to thephoto-alignment treatment. Accordingly, the overcoat film 203 at aportion not covered with the alignment film 113 is degraded byultraviolet radiation in photo-alignment.

The red color filter 201R is disposed between the overcoat film 203degraded by ultraviolet radiation and the light shielding film 202 tothereby block moisture penetrating through the degraded overcoat film203 by the red color filter 201R in the same manner as in the firstembodiment. Different from the first embodiment, the red color filter201R is not continuously formed to the edge portion in the embodiment.Instead, a region formed by removing the red color filter, that is, aportion A in FIG. 8 is disposed between the display region and the sealportion.

Due to the presence of the portion A, even when only one layer of thered color filter is formed in the seal portion, a step is formed for thealignment film 113, and therefore the step can be used as a stopperagainst the spreading of the alignment film. Moreover, the portion Aacts as a so-called liquid pool for the alignment film 113 and canreliably prevent the spreading of the alignment film 113 to the outsidetogether with the step.

In the embodiment, although a color filter formed in the seal portion isthe red color filter 201R, this is illustrative only. Another colorfilter, that is, the green color filter 201G or the blue color filter201B may be formed.

Fourth Embodiment

FIG. 9 is a cross-sectional view of the counter substrate 200 in thevicinity of an edge portion according to a fourth embodiment. In FIG. 9,the light shielding film 202, the red color filter 201R, the overcoatfilm 203, and the alignment film 113 are formed in this order on thecounter substrate 200. However, the red color filter 201R and the greencolor filter 201G are present between the overcoat film 203 and thelight shielding film 202 in the seal portion. The alignment film 113 issubjected to the photo-alignment treatment. Accordingly, the overcoatfilm 203 at a portion not covered with the alignment film 113 isdegraded by ultraviolet radiation in photo-alignment.

The red color filter 201R and the green color filter 201G are disposedbetween the overcoat film 203 degraded by ultraviolet radiation and thelight shielding film to thereby block moisture penetrating through thedegraded overcoat film 203 in the same manner as in FIG. 6 of the secondembodiment. Different from FIG. 6, the red color filter 201R is notcontinuously formed to the edge portion in the embodiment. Instead, aregion formed by removing the red color filter 201R, that is, theportion A in FIG. 9 is disposed between the display region and the sealportion.

Due to the presence of the portion A, a step formed in the vicinity ofthe seal portion corresponds to two layers of the red color filter 201Rand the green color filter 201G, and the height of the step can beincreased to from 2 μm to 4 μm. Accordingly, the alignment film 113spreading to the outside can be regulated more effectively. Moreover,the portion A acts as a so-called liquid pool for the alignment film 113and can more reliably prevent the spreading of the alignment film 113 tothe outside together with the step.

FIG. 10 is a cross-sectional view of the counter substrate 200 in thevicinity of an edge portion according to another aspect of the fourthembodiment. The configuration of FIG. 10 is the same as that of FIG. 9except that three layers of color filters of the red color filter 201R,the green color filter 201G, and the blue color filter 201B are presentbetween the overcoat film 203 and the light shielding film 202 in theseal portion.

In the configuration of FIG. 10, the red color filter 201R, the greencolor filter 201G, and the blue color filter 201B are disposed betweenthe overcoat film 203 degraded by ultraviolet radiation inphoto-alignment and the light shielding film 202 to thereby blockmoisture penetrating through the degraded overcoat film 203 in the samemanner as in FIG. 7 of the second embodiment. Different from FIG. 7, thered color filter 201R is not continuously formed to the edge portion inthe embodiment. Instead, a region formed by removing the red colorfilter 201R, that is, the portion A in FIG. 10 is disposed between thedisplay region and the seal portion.

Due to the presence of the portion A, a step formed in the vicinity ofthe seal portion corresponds to three layers of the red color filter201R, the green color filter 201G, and the blue color filter 201B, andtherefore the alignment film 113 spreading to the outside can beregulated more effectively. Since the step corresponds to three layers,the height of the step can be increased to from 3 μm to about 6 μm.Therefore, even when the viscosity of the alignment film 113 is low, thestep can sufficiently function as a stopper. Moreover, the portion Aacts as a so-called liquid pool for the alignment film 113 and can morereliably prevent the spreading of the alignment film 113 to the outsidetogether with the step.

In the embodiment as described above, it is possible to more reliablyprevent the influence of moisture penetrating through the degradedovercoat film 203 than the case of the third embodiment . Moreover,according to the configuration of the embodiment, the outer shape of thealignment film 113 can be more reliably defined.

In the embodiment, although the red color filter 201R and the greencolor filter 201G are sequentially stacked in FIG. 9, two layers ofcolor filters are not limited to those filters. Other color filters maybe stacked, and the stacking order may also be different. In FIG. 10,although color filters are stacked in the order of the red color filter,the green color filter, and the blue color filter, the stacking order ofcolor filters is not limited to this. The order can be arbitrarilydetermined depending on the manufacturing conditions of color filter.

Fifth Embodiment

FIG. 11 is a cross-sectional view of the counter substrate 200 in thevicinity of an edge portion according to a fifth embodiment of theinvention. In FIG. 11, the light shielding film 202, the red colorfilter 201R, the overcoat film 203, and the alignment film 113 areformed in this order on the counter substrate 200. In a seal portion,however, the light shielding film 202 and the overcoat film 203 areformed on the counter substrate 200, and the sealing material 15 isformed on the overcoat film 203. In FIG. 11, a color filter is notformed in the seal portion.

Also in the embodiment, the alignment film 113 is subjected to thephoto-alignment treatment. Accordingly, the overcoat film 203 at aportion where the alignment film 113 is not present is degraded byultraviolet radiation in photo-alignment. Moisture penetrates from thedegraded portion of the overcoat film in the same manner as in the firstto fourth embodiments.

A feature of the embodiment is in that a thickness of the overcoat film203 is greater at the seal portion than at a display region. In FIG. 11,the overcoat film 203 has a thickness of d2 at the seal portion and hasa thickness of d1 at the display region. As a ratio between thethickness d1 at the display region and the thickness d2 at the sealportion of the overcoat film 203, the thickness d2 is preferably equalto or greater than twice the thickness d1. However, the effect can beprovided even when the thickness d2 is equal to or greater than 1.5times the thickness d1. In the case where the thickness d2 is twice thethickness d1, when the thickness d1 at the display region is from 1 to 2μm, the thickness d2 is from 2 to 4 μm. An increase in thickness of theovercoat film 203 at the display region reduces the transmittance ratioof light, which reduces the brightness of a screen. Therefore, thethickness d1 of the overcoat film 203 at the display region must belimited to from 1 to 2 μm.

The overcoat film 203 not covered with the alignment film 113 isdegraded by ultraviolet radiation in photo-alignment. However, a regionin the vicinity of the surface is mainly degraded by ultravioletradiation, and ultraviolet radiation does not largely affect a depthportion of the film. In the embodiment, the overcoat film 203 isincreased in thickness at the portion directly irradiated withultraviolet radiation, so that the depth portion of the overcoat film203 is not damaged by ultraviolet radiation.

Accordingly, even in case the surface of the overcoat film 203 isdamaged by ultraviolet radiation to allow moisture to penetratetherethrough, the moisture is blocked at the depth portion of theovercoat film 203 and does not reach the light shielding film 202because the depth portion of the overcoat film 203 is not damaged.Accordingly, it is possible to prevent such a phenomenon that moisturereacts with the light shielding film 202 to cause peeling of the lightshielding film 202 or reduce the electrical resistance of the lightshielding film 202.

As a method for forming the light shielding film 202 having an increasedthickness only at the periphery, a half exposure technique can be used.In the case of using a positive photosensitive material for the overcoatfilm 203 for example, since the exposed portion is dissolved in adeveloper, such an exposure mask that the exposure amount of theovercoat film is reduced at the seal portion is used. Therefore, thethickness of the overcoat film can be increased only at the sealportion.

Also in the embodiment, since a step is formed between a thin portionand a thick portion of the overcoat film 203, the step can be used as astopper of the alignment film 113. The step formed in this case is from1 μm to 2 μm. Moreover, since a recessed portion formed between the edgeof the red color filter 201R and the step portion of the overcoat film203 can function as a liquid pool of the alignment film 113, therecessed portion can contribute to define the outer shape of thealignment film 113 together with the step of the overcoat film 203.

FIG. 12 is a modified example of the embodiment, which is a combinationof the embodiment and the configuration of the first embodiment. Thatis, the thickness of the overcoat film 203 is greater at a seal portionthan at a display region, and the red color filter 201R is disposedbelow the overcoat film 203. With this configuration, the effect ofprotecting the light shielding film 202 against the influence ofmoisture penetrating into the surface of the overcoat film 203 degradedby ultraviolet radiation can be assured more reliably.

FIG. 12 shows the example of the combination of the fifth embodiment andthe first embodiment, but the fifth embodiment can be combined with thesecond to fourth embodiments. When the fifth embodiment is combined withthe second to fourth embodiments, the height of the step acting as astopper of the alignment film 113 can be increased more, making itpossible to use an alignment film having a low viscosity.

Examples of forming methods of the alignment film 113 include, inaddition to flexographic printing, an inkjet method. When an alignmentfilm is formed by an inkjet method, the viscosity of the alignment filmmust be low. When the viscosity of the alignment film is low, thealignment film is likely to spread to the periphery, making it hard toaccurately define the forming range of the alignment film. In such acase, when the invention described in and after the second embodiment isused, a step is formed on the overcoat film 203, and therefore thespreading of the alignment film to the outside can be prevented. Thatis, since the use of the invention makes it possible to apply analignment film having a low viscosity, the choice of forming processesof the alignment film can be widened.

In the above-described embodiment, although the color filter formed inthe seal region is formed up to the edge of the counter substrate, thecolor filter may be terminated stepwise in front of the edge of thecounter substrate. With this configuration, the peeling of the colorfilter or the like at the edge of the substrate can be prevented.Moreover, instead of forming the color filter in the entire seal region,a part of the color filter can be removed in the seal region. Theremoved portion may have an island shape or a narrow stripe shapeparallel to a side of the substrate. With this configuration, a regionwhere the overcoat film is in contact with the light shielding film isformed in the part of the seal region. Moreover, the presence of a stepportion of the color filter in the seal portion increases the contactarea of the sealing material, making it possible to enhance the adhesivestrength between the sealing material and the counter substrate.Therefore, the reliability of the seal portion is improved.

While there have been described what are at present considered to becertain embodiments of the invention, it will be understood that variousmodifications maybe made thereto, and it is intended that the appendedclaims cover all such modifications as fall within the true spirit andscope of the invention.

What is claimed is:
 1. A liquid crystal display device comprising: afirst substrate; a second substrate; a sealing material fixing the firstsubstrate and the second substrate; a liquid crystal layer sealedbetween the first substrate and the second substrate; a plurality ofTFTs, a plurality of pixel electrodes, and a first alignment film whichare formed on the first substrate; and a light shielding film, a firstcolor filter, an overcoat film covering the first color filter, and asecond alignment film disposed between the overcoat film and the liquidcrystal layer, wherein the second alignment film is a photo alignmentfilm, wherein the overcoat film has a first region covered by the secondalignment film, and a second region not covered by the second alignmentfilm, and wherein the light shielding film, the first color filter, andthe overcoat film are stacked between the sealing material and thesecond substrate in the second region.
 2. The liquid crystal displaydevice according to claim 1, further comprising a counter electrodeformed on the first substrate, and wherein the liquid crystal layer iscontrolled by an electric field generated between the plurality of pixelelectrodes and the counter electrode.
 3. The liquid crystal displaydevice according to claim 2, wherein the first alignment film is a photoalignment film.
 4. The liquid crystal display device according to claim3, wherein the sealing material is in direct contact with the overcoatfilm in the second region.
 5. The liquid crystal display deviceaccording to claim 4, wherein, the first color filter is configured toprevent moisture entering the second region of the overcoat film fromreaching the light shielding film.
 6. The liquid crystal display deviceaccording to claim 1, wherein the first alignment film is a photoalignment film.
 7. The liquid crystal display device according to claim6, wherein the sealing material is in direct contact with the overcoatfilm in the second region.
 8. The liquid crystal display deviceaccording to claim 7, wherein, the first color filter is configured toprevent moisture entering the second region of the overcoat film fromreaching the light shielding film.
 9. The liquid crystal display deviceaccording to claim 1, further comprising a second color filer disposedbetween the overcoat film and the second substrate, and wherein thelight shielding film, the first color filter, the second color filter,and the overcoat film are stacked between the sealing material and thesecond substrate in the second region.
 10. The liquid crystal displaydevice according to claim 9, wherein the first alignment film is a photoalignment film.
 11. The liquid crystal display device according to claim10, wherein the sealing material is in direct contact with the overcoatfilm in the second region.
 12. The liquid crystal display deviceaccording to claim 9, further comprising a counter electrode formed onthe first substrate, and wherein the liquid crystal layer is controlledby an electric field generated between the plurality of pixel electrodesand the counter electrode.
 13. The liquid crystal display deviceaccording to claim 12, wherein the first alignment film is a photoalignment film.
 14. The liquid crystal display device according to claim13, wherein the sealing material is in direct contact with the overcoatfilm in the second region.